Pumping mechanism and pump inlet cover for use therein



April 1963 A. 1.. HARDY EIAI. 3,084,701

PUMPING MECHANISM AND PUMP INLET COVER FOR USE THEREIN Filed May 5, 19612 Sheets-Sheet 1 FWGJ INVENTORS ALBERT L. HARDY, DONALD s. cusnmsysTHoMAs a. TENKINS ozfw THE\ R ATTORNEY April 9, 1963 A. L. HARDY ETAI.3,

PUMPING MECHANISM AND PUMP INLET COVER FOR USE THEREIN Fil'd May 5, 19612 Sheets-Sheet 2 INVENTORS ALBERT L. HARDY, DONALD S. CUSHING 8 THOMASE. :rsmuus Wfm THEIR ATTORNEY United States Patent 3,084,701 PUMPINGMlEtCHANlSli i AND PUMP INLET OUVER FGR USE THEREHN Albert 11.. Hardy,Donald S. Qushing, and Thomas E.

Jenkins, Louisville, Ky, assignors to General Electric (Iompany, acorporation of New York Filed May 5, 1961, Ser. No. $,ii06 13 Claims.(Cl. 134-115) This invention relates to a pumping mechanism for liquidsand more particularly to a pumping mechanism for an automatic dishwasheremploying two pumps drawing liquid simultaneously from a single sumpspace.

Automatic dishwashers of the reaction spray type are generally designedto employ an operating cycle including a series of separate washing andrinsing operations in each of which a comparatively small amount ofwater is admitted to the washing compartment, circulated therein, andthen discharged from the machine. The washing water generally is sprayedupon the dishes in one or more spray streams under a pressure headprovided by a pumping mechanism contained in the dishwasher housing.This mechanism also effects a rapid draining of the soiled water fromthe dishwasher at the appropriate times in the cycle of dishwashingoperation. The conjoint use of two pumps in such a pumping mechanism,however, frequently results in an inefiicient pumping operation whenboth pumps have their inlets connected to the same sump space in thedishwasher tub. It is a purpose of the present invention to overcomethis disadvantage of automatic dishwashers through the employment of animproved pumping mechanism.

A general object of the invention is to provide a compact and efficientpumping mechanism having a plurality of commonly-driven pumps havinginlets communicating with a single liquid collecting space.

Another object is to provide a novel pump inlet cover for use with aslow speed axial flow pump having a low pump inlet head.

Another object is to provide an improved dishwasher having a single sumpspace and with a pumping mechanism having a plurality of pumps each ofwhich has a separated inlet communicating with that sump space.

A further object of the present invention is to design an axial flowpump with novel straining means to prevent foreign particles fromentering the pump.

A further object of the present invention is to design a vane type pumpwith a non-clogging inlet opening which will not accept hard foreignobjects but which will mulch and draw through the pump soft food waste.

A still further object of the present invention is to provide a combinedaxial flow pump and drain pump mechanism having a single driving means,with separating.

means between the two pumps to prevent the starvation of water and theforcing of air into the drain pump.

Further objects and advantages of the invention will become apparent asthe description proceeds, and the features of novelty which characterizethe invention will be pointed out with particularity in the claimsannexed to and forming a part of this specification.

In accordance with one aspect of this invention there is provided acompact pumping mechanism having a combined axial flow pump and a vanetype drain pump, the pumping mechanism being arranged to be positionedfor example, within a sump space at the lower part of the washingcompartment of a dishwashing structure. An upper pump housing enclosesthe axial flow pump and has an outlet which in the dishwashingapplication directs pumped liquid into a spray means; and a lower pumphousing encloses a vane type pump which may have two outlets, one ofwhich leads to a drain sewer and the other prising a suitable fifihifiiil Patented Apr. 9, 1963 ice of which leads to an additional spraymeans. Each of the pumps has an inlet communicating with the same sumpspace, and interposed between the respective pump housings is a specialpump inlet cover or separator which directs the flow of liquidsimultaneously to the pumps as well as performing other useful functionswhich will be explained hereinafter.

For a better understanding of the invention, reference may now be madeto the following description and accompanying drawings in which:

FIG. 1 is a side elevation view, with parts broken away and with partsin section, of a portable automatic dishwasher incorporating the presentinvention;

FIG. 2 is an enlarged side elevation view, with parts broken away andwith parts in section, of the pumping mechanism embodying the presentinvention and installed in the tub of a dishwasher;

FIG. 3 is a sectional plan view, with parts broken away, of the pumpinlet cover taken on line 3-3 of FIG. 2;

FIG. 4 is a top plan view of a centrifugal drain pump taken on line 44of FIG. 2, and

FIG. 5 is a side elevation view of the pump inlet cover.

Referring to FIG. 1 of the drawings, this invention has been shown inone form as applied to a portable automatic dishwasher comprising a tub9 defined by side walls 10, 11, 12 and 1G and having a bottom wall 14sloping downwardly to form a single sump space 15 for the collection ofwashing liquid. This liquid is supplied to the machine by any suitablemeans, not shown, and which supply forms no part of the presentinvention. In the type of dishwasher as shown, the tub is closed at itstop by a cover 16 hinged along one edge of the tub at 17 although theinvention, as will be understood, is in no way limited to a dishwasherhaving this type of access opening. The design is of equal usefulness insuch machines as the front-opening drop door type. A suitable latchmeans 18 may be provided at the front edge of the access cover and tubfor locking the cover in closed position during the operation of thedishwasher, and a cover push plate 19 serves to assist in the openingand closing of the cover. Within the front panel 20 of the cabinetstructure the controls of the machine may conveniently be mounted, and ahandle 21 for moving the machine on its casters 212 may likewise bemounted on this front panel. Disposed within the tub is an upper dishrack 23 and a separate lower dish rack 24. A suitable electrical heatingelement 25 may also be mounted within the bot tom of the tub 9 belowthese racks.

Referring now to FIGS. 2 and 4, the preferred pumping mechanism of thepresent invention is shown as comreversible electric motor 30 having arotor assembly and motor housing including an end bell 31. Fastened tothe end bell 31 is a series of three or more clamp-down bolts '32 forsecuring the stationary parts of the pumping mechanism to the motor. Themotor shaft 33 has rigidly attached thereto the impeller 34 of an axialflow pump rotatable on the same axis as the motor shaft and movablewithin an upper pump housing 35. Surrounding the motor shaft beneath theaxial flow pump impeller 34 is a centrally apertured lower drain pumphousing 29 having a floor portion 36, an upwardly extending wall portion37 and a fiat peripheral rim portion 38 extending over the bosses 31 ofthe motor and in clamping relation thereto. A pair of drain openings(not shown) from the back Wall portion of this housing lead intoconduits 45 and 46, later to be described.

Disposed within the lower drain pump housing 29 is a centrifugal pumpimpeller of drawn metal shape having pumping vanes 40 and 41 andarranged to pump efiiciently in either direction of motor rotation. Thispump impeller may be atfixed directly to motor shaft 33, or to anextension of the axial flow pump impeller 34 as shown, and in any eventis driven by the motor shaft as the motor rotates. Suitable liquidsealing means 43a formed as part of the drain pump impeller between thehousing 29 of the centrifugal pump and the motor shaft 33 also isprovided to prevent leakage from the pumping mechanism into the motor.Overlying the rim 38 of the centrifugal pump housing is a centrallyapertured pump cover plate 4-2 the aperture of which not only receivesthe motor shaft but also provides an annular opening 4-3 of smallclearance with respect to the rotating pump elements and serving as aninlet to the centrifugal pump and communicating with the sump space ofthe tub. This annular clearance 43 is of primary importance because itis so located and proportioned that it serves as a non-clogging inletopening for the drain pump. -It is possible for hard foreign objectssuch as hair pins, broken glass, screws, coins, etc. to fall into thedishwasher tub. These destructive objects are left out of the drain pumpby the small clearance opening 43 in the pump cover 42. In an automaticdishwasher it is desirable to be able to load the soiled dishes into themachine without first scraping or rinsing the food soil off.Accordingly, it is necessary that the drain pump accept large foodparticles such as corn kernels, potatoes, meat particles, carrots,spaghetti, etc. without plugging up the pump.

A filter screen might be used to keep out the hard particles but thesoft food particles would tend to plug the screen. This problem has beensolved by using a smooth rotating member (the shaft of the pump) inclose proximity with the sharp edge of the opening 43 in the pump cover42. Soft foods are then agitated and mulched until they reach a sizecapable of passing through the opening 43, but hard foreign objectscannot pass this opening.

Considering now FIG. 1, during rotation of the motor shaft in a firstdirection the above-described drain pump 2? upon receiving liquidthrough its inlet opening 43 pumps the same into a conduit 45 and uponrotation of the shaft in a second direction pumps the liquid into adrain conduit 46. This may be accomplished in accordance with theteachings of U.S. Patent No. 2,946,986 to Sholtes et al. which isassigned to the same assignee as is the present invention. This patentteaches a design using a fixed diverter member having a fioor portionconforming to the shape of the fioor 36 of the lower pump housing, aback wall supporting portion 47 conforming to the shape or" the backwall of that housing, and more importantly a pair of barrier portions 48and 49 spaced from each other and extending generally tangentiallytoward the central hub portion of the drain pump impeller but below theturning movement of the pump vanes 46 and 41, as best seen in FIGS. 2and 4.

Liquid pumped into conduit 4-5 serves a washing purpose and passesthrough a riser conduit 54) into a rotatable spray means 51 mounted tospray downwardly upon the dishes in the upper rack 23, as best describedand claimed in the copending application of Russell M. Sasnett, SerialNo. 853,894, filed November 18, 1959, and assigned to the same assigneeas is the present invention. Likewise, liquid pumped upwardly by theaxial flow pump impeller 34 serves a washing purpose as may best benoted from the construction of the upper pump housing 35. This pumphousing may include a tubular central body portion 52 terminating at alower edge 53 and having a plurality of peripherally spaced mountingfeet 54, 55, and 56 extending downwardly and outwardly of the centralbody portion. At its top edge the body portion 52 is reduced in diameterand is recessed to provide a circular seat 57 on which a hollow sprayarm 58, as seen in FIG. 1. is arranged to rotate under the reactionpropulsion force furnished by the stream of pumped liquid. A series ofradially spaced internal arch-like webs, one of which is seen at 59,support a stationary upturned bell shaped central boss 69 having a bolt61 passing therethrough. A

flanged nut 64 having an enlarged cylindrical portion is threaded overthe bolt. The flange of the nut with a fiber washer underneath overliesthe top surface of the spray arm, while the cylindrical portion fitsinto a clos fitting opening in the arm and serves as the rotatinghearing for the spray arm 58. This bolts also serves to secure to theboss 6% a downwardly mounted stationary diffuser member 62 havingradially spaced curved vanes 63 disposed adjacent the discharge end ofthe vanes of the impeller 34 of the axial flow pump. This diffuser isimportant to the design of the axial flow pump impeller 34 in that ittakes the swirling water from the impeller 34 and straightens it out toan axial flow for supplying the high velocity wash water to the reactionspray system. An apertured disc or reinforcing plate 66 is fastenedwithin the spray arm so that a vertical supplemental spray tube 65communicating with the interior of the spray arm 53 may be held in placeby fastening screw means 67. It should be noted that the upturnedbell-shaped boss 60 serves as a flow diverter to direct most of thewater received from the axial flow pump away from vertical spray tube 65and sidewise into the interior of the rotating spray arm 58.

In general, the capacity of the axial flow pump, which furnishes liquidfor the spraying upwardly over the dishes on both of racks 23 and 24, ismuch greater than the capacity of the above-described centrifugal drainpump 29, and a large inlet to the axial flow pump is required. it hasbeen found, however, that the rotation of the axial fiow pump impellerin its upward pumping direction tends to starve the drain pump ofliquid, and the rotation of the axial flow pump impeller in the reversedirection, i.e., in a downwardly pumping direction, tends to force airinto the inlet of the drain pump. in addition, the use of the axial flowpump with a low pump inlet head presents problems of vortex effects inthe liquid flow from the sump space 15 into the pump and necessitatessome special provision for establishing a steady pump how without largesurges as when the dishwasher is operated with a comparatively smalltotal water fill of between seventeen and twenty-two pints of water.Moreover, malfunctioning of the pumping and spraying elements due to thepresence of foreign objects or large food particles or the like must beavoided.

The present invention provides a solution to these problems by includingin the pumping mechanism between the axial flow pump and the drain pumpa fixed flowdirecting pump inlet cover 68, one suitable form of which isshown in FIG. 5. This cover fits around the pump impeller 34- and mayinclude an uppermost rim portion 70 merging with the impeller with acircular concave body portion 71 extending from that upper rim 70 to alower generally circular larger diameter outer periphery 72 of thecover. Extending downwardly and interiorly of the rim portion 70 is atruncated conical Wall portion or bushing 73 closely embracing theconical shaft of the impeller 34 of the axial flow pump and having aclosefitting but free running lip '74 in engagement with the impeller toprevent bypassing of air and liquid. Adjacent the outer periphery 72 ofthe cover is a plurality of vertically extending arcuately arrangedgrid-like wall portions 75, 76 and 77 (FIGS. 3 and 5) projectingupwardly from the lower periphery 72 of the body portion and beingarranged outside the pump housing 35 to leave an open inlet space 78(FIG. 2) between the grid-like wall portions and the lower edge 53 ofthe upper pump housing 35. A plurality of vertical, radially spacedbafiie or web portions '79 along the circular concave surface of thebody portion of the cover connect the upper rim 70 to the wall portions75, 76 and 77 and serve to reinforce the cover as well as to straightenthe flow of liquid along that concave surface while improving theperformance or output of the pump by preventing vortex effects of theliquid at the inlet to the axial flow pump impeller. Intermediate theadjacent grid-like wall portions, recesses or slots 80, 81 and %2 (FIG.3) are provided for reception of the respective mounting legs 54, 55 and56 of the upper pump housing 35. Thus, with the described pump inletcover held in place by these legs and with these legs secured by bolts32 to the end bell 31 of the motor housing and with the entire pumpingassembly clamped in sealed relation to the lower wall 14 of the tub, asby the split clamping ring 83 seen in FIG. 2, a firm stationary mountingof the pump inlet cover for the axial flow pump, is obtained. Moreover,the fastening of the pump housing directly and rigidly to the end bellof the motor housing ensures accurate concentricity of the pump elementswith respect to the motor which permits smaller manufacturingtolerances, improved efficiency, longer life expectancy of the rotatingparts, and a less severe shaft sealing problem.

The recesses 80, 81 and 82 of the grid-like wall portions thus describedare provided with depending feet having hold-down seats or ledges ontheir upper surfaces, one of which is seen at 84 in FIG. 5, and againstwhich an inner ledge on the corresponding mounting leg 56 of the upperpump housing abuts. Projecting downwardly from these seats are shortpegs 85, 86 adapted in turn to bear against the upper surface of thepump cover plate 42 for the drain pump 29 and to maintain that cover inproperly centered position. A suitable gasket 9% underlies the peripheryof the pump cover 42 to prevent the leakage of liquid therefrom. Thegrid-like wall portions, moreover, are formed with a plurality ofindividual struts or posts spaced from each other at a suitable distanceas shown at 87, S8 and 89 to afford comparatively free flow of liquidand soft food therebetween, but to intercept large size hard objectswhich may enter the tub inadvertently.

' As will now be apparent, the comparatively large inlet to the axialfiow pump impeller 34, through both the space '78 and through thefence-like wall portions 75, 76 and 77, communicates with the sump space15; and at the same time the annular opening 43 below the body portionof the axial flow pump inlet cover 68 that Serves the drain pumpcommunicates with the same sump space. As the motor turns in a firstdirection (counterclockwise) to cause the axial flow pump impeller 34 todraw liquid through its inlet, such liquid is trapped between thevertical stationary baffies 79, and the radial movement thereof isconverted into a steady flow generally axially of the axial flow pump.At the same time, the concave surface of the inlet member directs theflow of the incoming liquid from anupper level of the sump space, andthe lower portion of that same inlet member is so positioned that theflow of incoming liquid to the drain pump may take place from thelowermost level of the sump space. The liquid passing under the inletcover 68 and into the drain pump thus submerges that pump and thepumping action of the larger axial flow pump therefore is unable tostarve the smaller drain pump. As the motor turns in its seconddirection (clockwise), the axial flow pump may draw in air from thespray arm 58 and tube 65. and discharge the same laterally through space78 or through the fence-like wall portions of the cover, but due to thepresence of the concave upper portion of the cover 68 such air isdirected away from the inlet 43 of the drain pump and will not interferewith the functioning of the drain pump during its draining action.

Having described above a novel pump mechanism with regards to thedetails of a preferred embodiment, it will readily be apparent to thoseskilled in this art that the pump inlet cover of this invention can beused alone with the axial flow pump without the incorporation of thelower drain pump. A reversible drive motor has been described, but amotor having but one direction of rotation could be used if a divertervalve were used with the two outlets of the drain pump to control theflow of liquid therethrough. In the drawing, the drain pump isillustrated as a centrifugal type pump but other vane type pumps couldalso be used to advantage here.

The production model of this invention handles a water load of betweenseventeen and twenty-two pints of water at a pumping rate in the washingdirection of fifty-eight gallons per minute with a one-third horsepowermotor at a load of seven hundred watts and a speed of 3450 r.p.m.

While we have shown and described particular embodiments of theinvention, we do not desire the invention to be limited to theparticular constructions disclosed, but rather we intend by the appendedclaims to cover all modifications within the true spirit and scope ofthe invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. In a dishwasher having a washing tube with a sump space forcollecting washing liquid, a pumping mechanism including an axial flowpump having an inlet communicating with said space, a vane pumppositioned below said axial flow pump and having an inlet communicatingwith said space, means for driving said pumps, an

upper pump housing enclosing said axial flow pump and having an outlet,a lower pump housing enclosing said vane pump and having an outlet, anda flow-directing pump inlet cover interposed between the respectivehousings of said pumps, said cover having an upper portion arranged todirect liquid from an upper level of said space into the inlet of saidaxial fiow pump, and said cover having a lower portion arranged for flowof liquid thereunder from a lower level of said space into said vanepump thereby to relieve said vane pump from liquid starving as liquid issimultaneously supplied from said sump space to each of said pumps.

2. Apparatus as defined in claim 1 wherein said upper portion of saidcover is concave and includes substantially vertical baffles projectingradially of the axis of said axial flow pump, said baiiies being spacedfrom each other and positioned to prevent swirling of liquid enteringsaid axial flow pump.

3. Apparatus as defined in claim 1 wherein said lower portion of saidcover includes mounting feet radially spaced from each other and held instationary position by said upper pump housing, the spaces between saidfeet' serving to communicate the inlet of said vane pump with said sumpspace.

4. A flow-directing cover for the inlet of an axial flow pump comprisinga generally annular shaped member having a central aperture forreceiving the shaft of said pump and defining an inner rim of saidcover, a concave body portion extending from said rim to the peripheryof said member, an apertured wall portion generally parallel to the axisof said aperture and projecting from said body portion on its concaveside adjacent the periphery of said member, and baffles spaced from eachother and extending radially along said concave body portion betweensaid rim and said wall portion whereby liquid flowing through said Wallportion for entrapment of objects carried by said liquid may pass acrosssaid concave surface between said baffles and may be changed indirection from a flow generally spirally of said pump shart to a flowgenerally parallel to said pump shaft.

5. A cover as defined in claim 4 including a hollow bushing portion forsurrounding said shaft, said bushing portion terminating at one end atsaid inner rim and having a sealing member adjacent its other end forcontact with said shaft.

6. In a dishwasher having a washing tub with a sump space for collectingwashing liquid, a pumping mechanism comprising a reversible motor havinga shaft arranged to rotate in a first direction and in a second direction, an axial flow pump driven by said shaft and having an inletcommunicating with said space, a centrifugal pump driven by said shaftand positioned below said axial flow pump and having an inletcommunicating with said space, an upper pump housing enclosing saidaxial flow pump and having an outlet, :1 lower pump housing enclosingsaid centrifugal pump and having a first outlet discharging into saidtub and a second outlet discharging from said tub, and a flow-directingpump cover interposed between the respective housings of said pumps,said cover having a concave upper portion arranged to direct liquid froman upper level of said space into the inlet of said axial flow pump whensaid shaft is rotating in said first direction and to direct air pumpedby said axial flow pump when said shaft is rotating in said seconddirection away from the inlet to said centrifugal pump, said coverhaving a lower portion arranged for flow of liquid thereunder from alower level of said space into the inlet of said centrifugal pump whensaid shaft is rotating in either direction.

7. A washing compartment having a sump in the bottom thereof, an openingin the bottom of the sump, a pumping mechanism supported in the saidopening, said pumping mechanism including a single driv motor, avertical shaft driven by the motor, an axial flow pump supported withinthe sump and having an impeller mounted on the top end of the motorshaft, a vane pump located beneath the sump for use in draining thesump, the vane pump also having an impeller driven by the said motorshaft, and a pump inlet cover surrounding the motor shaft and fixed inposition slightly above the bottom of the sump, the inlet for the axialfiow pump being above the pump inlet cover while the inlet for the vanepump is below the said inlet cover, a supplementary Washing systemwithin the compartment, the vane pump having two separately controlledoutlets, a first outlet connected with the supplementary washing systemand a second outlet for draining the sump of liquid, so that during oneoperation of the pumping mechanism the axial flow pump recirculatesliquid within the compartment While the vane pump delivers liquidthrough its first outlet only to the supplementary washing system, thesecond operation of the pumping mechanism preventing said axial flowpump from recirculating liquid within said compartment and causing thevane pump to deliver liquidthrough its second outlet for draining thesump completely.

8. A Washing compartment as recited in claim 7 wherein the single drivemotor is a reversible motor which turns in one direction for thefirst-mentioned operation of the pumping mechanism and in the oppositedirection for the second-mentioned or draining operation of the pumpingmechanism.

9. A washing compartment as recited in claim 7 wherein the top surfaceof the said pump inlet cover is a circular concave surface which isdirected horizontally inwardly into the axial fiow pump and thenupwardly so that the liquid will be guided in its fiow 'therethrough,and a series of vertical radially spaced baflles rising from the topsurface of the said cover for straightening out the flow of liquid andprevent swirling as it enters the axial flow pump.

10. A washing compartment as recited in claim 9 wherein the top surfaceof the pump inlet cover also includes a grid-like member adjacent theperiphery of said cover for screening large foreign objects fromentering the axial flow pump.

11. A Washing compartment as recited in claim 7 wherein the inlet forthe vane pump is an annular opening having a slight clearance from thedrive shaft of the motor so that large hard objects may not pass throughthe opening but soft food soil will accumulate in the vicinity of theopening during the draining operation, the soft food being agitated bythe rotation of the drive shaft for mulching the food until the food isdrawn through the opening and driven from the vane pump.

12. A washing compartment having a sump in the bottom thereof, anopening in the bottom of the sump, a pumping mechanism supported Withinthe sump above the opening and having an inlet adjacent the saidopening, means located below the washing compartment for driving thepumping mechanism, said means including a vertical shaft extendingthrough the sump opening and having an impeller of an axial flow pump onthe top end thereof, a pump housing surrounding the impeller, a pumpinlet cover supported in the pump inlet and fixed in position withrespect to the pump housing, the pump inlet extending substantiallycompletely around the pump housing, the inlet cover having a circularconcave upper surface for directing liquid radially into the pumphousing and then axially to the pump impeller, vertically-extendingradiallyspaced baffles rising from the concave surface to straighten outthe flow of liquid as it is drawn into the impeller, a filtering wallmeans arranged on the periphery of the pump inlet cover between thecover and the pump housing to govern the particle size of foreign matterentrained in the liquid that will pass through the pump, and pump inletcover closely embracing the pump impeller to prevent air and liquidpassing therebetween.

13. A Washing compartment as recited in claim 12 wherein the filteringwall means comprises a series of vertical posts arranged around theperiphery of the pump inlet cover, and the center of the cover is in theshape of a hollow inverted truncated cone, the pump impeller having alower converging shank for close-fitting engagement with the hollow coneof the pump cover to prevent air and liquid passing therebetween.

References Qited in the file of this patent UNITED STATES PATENTS1,637,376 Gibney Aug. 2, 1927 1,817,328 Weimers Aug. 4, 1931 1,942,452Rogers Jan. 9, 1934 2,023,107 Stoddard Dec. 3, 1935 2,054,797 FranklinSept. 22, 1936 2,250,314 Rocke July 22, 1941 2,257,436 Walker Sept. 30,1941v 2,305,136 Campbell Dec. 15, 1942 2,729,219 Smith Jan. 3, 19562,946,286 Sholtes et al July 26, 1960 2,959,179 Sasnett et al Nov. 8,1960 FOREIGN PATENTS 649,783 Great Britain Jan. 31, 1951

7. A WASHING COMPARTMENT HAVING A SUMP IN THE BOTTOM THEREOF, AN OPENINGIN THE BOTTOM OF THE SUMP, A PUMPING MECHANISM SUPPORTED IN THE SAIDOPENING, SAID PUMPING MECHANISM INCLUDING A SINGLE DRIVE MOTOR, AVERTICAL SHAFT DRIVEN BY THE MOTOR, AN AXIAL FLOW PUMP SUPPORTED WITHINTHE SUMP AND HAVING AN IMPELLER MOUNTED ON THE TOP END OF THE MOTORSHAFT, A VANE PUMP LOCATED BENEATH THE SUMP FOR USE IN DRAINING THESUMP, THE VANE PUMP ALSO HAVING AN IMPELLER DRIVEN BY THE SAID MOTORSHAFT, AND A PUMP INLET COVER SURROUNDING THE MOTOR SHAFT AND FIXED INPOSITION SLIGHTLY ABOVE THE BOTTOM OF THE SUMP, THE INLET FOR THE AXIALFLOW PUMP BEING ABOVE THE PUMP INLET COVER WHILE THE INLET FOR THE VANEPUMP IS BELOW THE SAID INLET COVER, A SUPPLEMENTARY WASHING SYSTEMWITHIN THE COMPARTMENT, THE VANE PUMP HAVING TWO SEPARATELY CONTROLLEDOUTLETS, A FIRST OUTLET CONNECTED WITH THE SUPPLEMENTARY WASHING SYSTEMAND A SECOND OUTLET FOR DRAINING THE SUMP OF LIQUID, SO THAT DURING ONEOPERATION OF THE PUMPING MECHANISM THE AXIAL FLOW PUMP RECIRCULATESLIQUID WITHIN THE COMPARTMENT WHILE THE VANE PUMP DELIVERS LIQUIDTHROUGH ITS FIRST OUTLET ONLY TO THE SUPPLEMENTARY WASHING SYSTEM, THESECOND OPERATION OF THE PUMPING MECHANISM PREVENTING SAID AXIAL FLOWPUMP FROM RECIRCULATING LIQUID WITHIN SAID COMPARTMENT AND CAUSING THEVANE PUMP TO DELIVER LIQUID THROUGH ITS SECOND OUTLET FOR DRAINING THESUMP COMPLETELY.